The overall purpose of this research proposal is to examine the role of the limbic system in hypothalamic aggression. The first phase of the research project attempts to determine how the limbic system and related structures modulate quiet biting and affective attack behavior elicited by electrical stimulation of the hypothalamus. The principal paradigm involves presentation of paired trials of single (hypothalamic) and dual (limbic plus hypothalamic) stimulation. Differences in response latency between paired trials of single and dual stimulation provide the basis for determining the effects of limbic stimulation upon hypothalamic aggression. The limbic structures thus far considered include the hippocampus, septal area, cingulate gyrus, pyriform cortex, and prefrontal cortex. In this proposal structures to be studied include the basal forebrain region and the mammillary bodies. A second phase of this project will attempt to determine the origin and distribution of the fibers of the hippocampus, septal area, and basal forebrain which may relate to the control of attack behavior. A third phase will attempt to determine the neurophysiological relationships between hypothalamic sites producing attack behavior and neurons in the limbic system and midbrain. Other studies will attempt to study the input-output relationships of the subiculum. A fourth phase will attempt to determine the possible neurotransmitters involved in quiet biting and affective forms of aggression.